1. Field of the Invention
The present invention relates to a data compression apparatus adapted for use in an electronic image file or the like, and more particularly to such apparatus for forming compressed data by applying a compression process of a determined logic to input data.
2. Description of the Prior Art
There is already known a technology for compressing binary digital data of high redundancy, such as digital image signals read from an object, according to a determined logic. Such compression technology is used for reducing the quantity of data and shortening the transmission time, for example in so-called facsimile apparatus for image transmission through a telephone line.
Also there are have recently been proposed electronic image files utilizing laser disks or magnetic disks capable of storing a large quantity of image data, and the use of such compression technology in such apparatus allows one to effectively increase the memory capacity of these memory media.
Among such data compression processes is particularly well known the modified Huffman process (M-H process), in which the original image data are converted into modified Huffman codes (M-H codes) according to the measurement of consecutive number of white or black signals in the original image data, or of so-called run length.
Said M-H codes have variable code length ranging from 2 bits to 13 bits according to the run length. Consequently it is not easy to pack such M-H codes into the units of combined bytes or of words.
In the aforementioned facsimile apparatus in which the scanning for reading the original image need not be of a very high speed and the mechanical operation for original scanning can be conducted intermittently, the connection of M-H codes has conventionally been conducted at a low speed for example with a microcomputer and the scanning of a succeeding line is started at the time of the signal packing or transmission of a preceding line.
However high-speed processing and transmission of data have come to be desired recently for the electronic image file and the like, and such demands require high-speed original reading and M-H data processing on real-time basis. Conventional data processing methods have however not been able to completely satisfy such demands, thus being a bottleneck in achieving high-speed processing in the apparatus.